A great variety of parasites are dependent on freshwater environments. The digenetic trematodes, or flukes, are a prominent example whose members usually have free-swimming aquatic forms and whose hosts are often freshwater organisms. Digeneans are the agents of several well-known human diseases including schistosoniiasis, echinostomiasis, and cercarial dermatitis. The diseases of wildlife are generally less known. However, digeneans have received close attention recently because of their suspected role in outbreaks of amphibian deformities. We propose a multi-tier approach to understanding the influence of human induced changes on vector borne disease in host amphibians. Our goal is understand key forms of anthropogenic: change that influence disease outbreaks and to develop predictive models for the emergence and dynamics of amphibian trematode parasites in anthropogenically-influenced environments. We propose to complete a large-scale, multi-regional survey of wetlands across the northeastern United States and a set of long-term experiments involving manipulation of whole wetlands. The survey will be conducted in 4 regions and, in each, will be stratified across a gradient of human development. In each wetland surveyed we willcollect information on physical and chemical conditions and will sample resident snails and amphibians. The identity and burden of trematodes will be determined for each animal collected. Experiments will be conducted simultaneously in two regions with each experiment lasting for five years. In one experiment, we will alter the light environment. In a second, we will manipulate nutrient concentrations. In a third experiment, we will alter wetland hydro-period. Each manipulation will mimic changes believed to be associated with anthropogenic disturbances of wetlands. In each experiment, we will alter a subset of entire ponds from baseline conditions and compare the dynamics of snails, trematodes, and amphibians subsequently. Finally we plan to develop quantitative models in order to make predictions about the effects of urbanization on the disease dynamics. Development of mathematical models for these trematode systems will provide a template for studies of other snail borne diseases with similar community modules, for example, schistosomiasis.